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Subject: Re: [PATCH v6] ARM: dts: wheat: Fix ADV7513 address usage
To:     Simon Horman <horms@verge.net.au>
Cc:     linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org,
        Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Magnus Damm <magnus.damm@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Russell King <linux@armlinux.org.uk>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        "moderated list:ARM PORT" <linux-arm-kernel@lists.infradead.org>
References: <1521754240-10470-1-git-send-email-kieran.bingham+renesas@ideasonboard.com>
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 <a771042b-f63a-d00f-73a1-91a7e6089fe4@ideasonboard.com>
 <20180326083143.r6jz6csckd4ljnpu@verge.net.au>
From:   Kieran Bingham <kieran.bingham@ideasonboard.com>
Organization: Ideas on Board
Message-ID: <d2c5d935-da1f-038b-a0e6-ce390273e21a@ideasonboard.com>
Date:   Mon, 26 Mar 2018 10:04:24 +0100
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Hi Simon,

On 26/03/18 09:31, Simon Horman wrote:
> On Fri, Mar 23, 2018 at 09:16:13PM +0000, Kieran Bingham wrote:
>> Hi Simon,
>>
>> On 23/03/18 08:51, Simon Horman wrote:
>>> On Thu, Mar 22, 2018 at 09:30:40PM +0000, Kieran Bingham wrote:
>>>> The r8a7792 Wheat board has two ADV7513 devices sharing a single I2C
>>>> bus, however in low power mode the ADV7513 will reset it's slave maps to
>>>> use the hardware defined default addresses.
>>>>
>>>> The ADV7511 driver was adapted to allow the two devices to be registered
>>>> correctly - but it did not take into account the fault whereby the
>>>> devices reset the addresses.
>>>>
>>>> This results in an address conflict between the device using the default
>>>> addresses, and the other device if it is in low-power-mode.
>>>>
>>>> Repair this issue by moving both devices away from the default address
>>>> definitions.
>>>
>>> Hi Kierean,
>>>
>>> as this is a fix
>>> a) Does it warrant a fixes tag?
>>>    Fixes: f6eea82a87db ("ARM: dts: wheat: add DU support")
>>> b) Does it warrant being posted as a fix for v4.16;
>>> c) or v4.17?
>>
>> Tricky one, yes it could but this DTS fix, will only actually 'fix' the issue if
>> the corresponding driver updates to allow secondary addresses to be parsed are
>> also backported.
>>
>> It should be safe to back port the dts fix without the driver updates, but the
>> addresses specified by this patch will simply be ignored.
> 
> In that case I think its safe to add the fixes tag and take the DTS patch
> via the renesas tree. Perhaps applying it for v4.18 and allowing automatic
> backporting to take its course is the cleanest option.
> 
>> Thus if this is marked with the fixes tag the corresponding patch "drm: adv7511:
>> Add support for i2c_new_secondary_device" should also be marked.
>>
>> It looks like that patch has yet to be picked up by the DRM subsystem, so how
>> about I bundle both of these two patches together in a repost along with the
>> fixes tag.
>>
>> In fact, I don't think the ADV7511 dt-bindings update has made any progress
>> either. (dt-bindings: adv7511: Extend bindings to allow specifying slave map
>> addresses). The media tree variants for the adv7604 have already been picked up
>> by Mauro I believe though.
>>
>> I presume it would be acceptable for this dts patch (or rather all three patches
>> mentioned) to get integrated through the DRM tree ?
> 
> Unless there is a strong reason I would prefer the dts patch to go via
> my tree. The reason is to avoid merge conflicts bubbling up to Linus,
> which really is something best avoided.

That's perfectly fine with me.

Feel free to add:

Fixes: f6eea82a87db ("ARM: dts: wheat: add DU support")

as you suggested when you apply, or alternatively let me know if you need a repost.

Regards
--
Kieran